Bluetooth Low Energy (BLE) relates to Bluetooth wireless radio technology. It has been designed for low-power and low latency applications for wireless devices within short range. Today, BLE applications can be found from healthcare, fitness, security, smart energy, industrial automation and home entertainment. However, BLE is not limited only those, but increasingly more new application utilizing BLE technology are designed.
The difference between BLE and classic Bluetooth is that the BLE devices consume remarkably less power for communication than classic Bluetooth devices. In addition, the BLE is able to start the data transmission much quicker than the classic Bluetooth. This makes it possible to have BLE devices constantly on and to communicate intermittently with other devices.
In BLE technology, one or more so called slave devices can be connected to a master device. To let the master know about the slave devices before connection, the slave devices (or at that point “advertisers”) periodically, at pseudo-random intervals, pass advertisement packets which the master device (also known as scanner device, i.e., “scanner”) is scanning. Depending on the type of advertisement packet sent by a slave device, the master device may respond to the received advertisement packet by requesting a connection with the slave device, or may respond by requesting further information from the advertising device.
The BLE specification (Bluetooth Specification Versions 4.0, 4.1, 4.2) requires that individual BLE advertisement packets be transmitted periodically from a BLE advertising device in advertising mode at T_advEvent intervals. T_advEvent consists of two components, advInterval which is a fixed time value, and advDelay which is a pseudorandom delay time for adding pseudorandom jitter of from 0 to 10 milliseconds. Conventional devices scanning for transmitted advertisements packets do not know what pseudorandom delay time value (advDelay) is being added to the regular time interval value (advInterval) for any given packet. Therefore, after receiving an advertisement packet, a conventional scanning device must scan continuously to receive the next advertisement packet, which consumes large amounts of power.